This application is based on Japanese Patent Application No. 2002-76194 filed on Mar. 19, 2002, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary compressor for a vehicle. The rotary compressor is suitably used for a vacuum pump driven by an engine, or a power pump mounted on a power steering device for a vehicle.
2. Related Art
As shown in FIGS. 3 and 4, a rotary compressor 101 includes a housing 102, a rotation shaft 103, a rotor 104 and vanes 105. The housing 102 is arranged adjacent to an AC generator (not shown). An intake port 106 is provided at an upper side of the housing 102, and a discharge port 107 is provided at a lower side of the housing 102. The rotation shaft 103 extends from a front frame of the AC generator into the housing 102 to be used also as a rotation shaft of the AC generator. As shown in FIG. 4, vane recesses 140 extending radially are provided in an outer peripheral surface of the rotor 104, and the vanes 105 are disposed to be movably held in the vane recesses 140. On the other hand, the rotation shaft 103 is coupled to an engine through a V-belt and a pulley, on the side of the AC generator. Therefore, in a case where the rotation speed of the engine is high, such as in a vehicle travelling on a speedway, the rotation speed of the rotation shaft 103 becomes higher. Conversely, in a case where the rotation speed of the engine is low, such as in a vehicle travelling on an urban road, the rotation speed of the rotation shaft 103 becomes lower. On the other hand, when the vehicle is traveling in the urban road, the using frequency of a brake connected to the rotary compressor 101 becomes higher as compared with the case where the vehicle is traveling in the speedway. However, in the rotary compressor 101, the rotor 104 is integrally connected to the rotation shaft 103. Accordingly, when the rotation speed of the engine is high, the rotor 104 always rotates so that a sufficient negative pressure (vacuum) is applied. That is, useless rotation is performed in the rotor 104. Therefore, load applied to the engine is increased, and fuel consumption efficiency of the vehicle is deteriorated.
Further, in the high-rotation speed of the engine, the rotation speed of the rotor 104 is high as compared with that in the low-rotation speed of the engine. Therefore, sliding members of the rotary compressor 101 are required to have resistant to attrition, friction heat and centrifugal force, due to the high-speed rotation.
On the other hand, if the rotary compressor 101 is used for a power steering device, when the rotation speed of the engine is low, the using frequency of a vehicle steering is higher as compared with a case where the rotation speed of the engine is high. Accordingly, even when the rotary compressor 101 is used for the power pump of the power steering device, the problems described above in the vacuum pump may be caused.
In view of the above-described problems, it is an object of the present invention to provide a vehicle rotary compressor operated by a driving source, which can effectively restrict useless rotation in a high-speed rotation of the driving source.
It is another object of the present invention to provide a vehicle rotary compressor that can reduces a request of durability in slidable members.
According to the present invention, in a rotary compressor for a vehicle includes a housing having an approximate cylindrical inner peripheral surface, a rotor that is rotatable eccentrically to the inner peripheral surface of the housing, a plurality of vanes disposed radially in an outer peripheral surface of the rotor to be slidable on the inner peripheral surface of the housing, a rotation shaft that is disposed to transmit a rotation force of a driving source to the rotor, and a connection member that is disposed to be connected to the rotation shaft and the rotor such that the rotation force of the rotation shaft is transmitted to the rotor. In the rotary compressor, the connection member is connected to the rotation shaft so that the rotation force is transmitted from the rotation shaft to the rotor when a rotation speed of the rotation shaft is lower than a predetermined value, and the connection member is separated from the rotation shaft so that the rotation force from the rotation shaft to the rotor is interrupted when the rotation speed of the rotation shaft is equal to or higher than the predetermined value. Accordingly, when the rotation speed of the rotation shaft is equal to or higher than the predetermined value, the operation of the rotary compressor is stopped. Therefore, it can restrict useless load from being applied to the engine, and fuel consumption efficiency can be improved. Further, the rotary compressor does not rotate with a high rotation speed. Therefore, slidable members of the rotary compressor are unnecessary to have durability to attrition, fraction heat and centrifugal force, due to the high-rotation speed. Here, the sladable members include at least the housing, the rotor and the vanes. Accordingly, materials for forming the rotary compressor can be readily selected.
According to the present invention, a biasing member for biasing the connection member toward the rotation shaft is provided, and the rotor has a receiving portion for receiving the connection member and the biasing member. Therefore, when the rotation speed of the rotation shaft is lower than the predetermined value, the connection member is biased toward the rotation shaft by the biasing force of the biasing member, and the connection member can be connected to the rotation shaft. Thus, the rotary compressor can be operated. On the other hand, when the rotation speed of the rotation shaft is equal to or higher than the predetermined value, centrifugal force applied to the connection member becomes larger than the biasing force of the biasing member. Therefore, the connection between the connection member and the rotation shaft is interrupted, and the operation of the compressor is stopped. Because a rotation transmission mechanism of the rotary compressor is constructed by the balance between the centrifugal force and the biasing force of the biasing member, the rotation transmission mechanism has a simple structure. Thus, the number of the rotary compressor can be reduced while reliability thereof can be improved.
Preferably, the rotation shaft has thereon a connection portion having an engagement portion, and the engagement portion is provided to be engaged with the connection member in a rotation direction of the rotation shaft so that the rotation force of the rotation shaft is transmitted to the rotor. Therefore, the rotation force of the rotation shaft can be transmitted to the rotor by the engagement between the connection member and the engagement portion provided on the rotation shaft. Further, the connection portion is provided on the rotation shaft such that a distance xe2x80x9crxe2x80x9d between a center of the rotation shaft to the connection portion is gradually increased in the rotation direction of the rotation shaft. Therefore, it can effectively restrict a large collision from being caused between the connection member and the connection portion of the rotation shaft when the rotation speed of the rotation shaft is changed from a speed higher than the predetermined value to a speed lower than the predetermined speed.